As a method for achieving a reduction in bit cost and increasing the memory performance of nonvolatile semiconductor memory devices, a method of scaling down the dimensions of a memory cell is effective. However, scaling down of a memory cell is becoming technically difficult.
Thus, it has been proposed to use organic molecules for a charge memory layer. Organic molecules can be formed by organically combining various molecular structures and substituents. Thus, desired electrochemical properties can be provided. Also, the smallness of their building units provides the possibility of being able to achieve scaling down of a memory cell.
For a nonvolatile semiconductor memory device using organic molecules in a charge memory layer, a further improvement in charge retention characteristics is desired.